The worldwide industrial revolution of the past two centuries changed the energy scene from essentially total global reliance on renewable energy to global reliance practically entirely on fossil energy forms, with the consequence of elevated carbon dioxide content in the atmosphere with its potential for deleterious climate change. Consequently, worldwide concern exists toward developing means to protect the atmosphere by capturing carbon dioxide produced from fossil-fuel combustion in order to avoid its emission to the atmosphere. Two technologically-feasible options exist for avoiding emission to the atmosphere. One option lies in storage of captured carbon dioxide under high-pressure in underground geological formations and accepting the costs without compensating revenues. The other option lies in the use of captured carbon dioxide for enhancing the production of petroleum crude oil through its injection under high pressure into mature oil fields with the receipt of compensating revenues. These two options generally are referred to as sequestration of captured carbon dioxide.
The photosynthesis process by which microalgae can be cultivated from captured carbon dioxide involves a series of complex chemical reactions in which carbon dioxide, water, nutrients, and insolation are converted to an oil-rich algae biomass and essentially pure oxygen gas. Through recycling, the carbon dioxide is completely consumed.
Considerable intensive worldwide research and development activity currently exists aimed at two modes of algae cultivation: one in open ponds and the other in enclosed structures known as photobioreactors. The open-pond mode can be characterized as requiring large land areas in terms of their output, as subject to adverse impact in the form of invasion by unwanted algae species, as impacted by the effects of wind, evaporation, storms, and as losses of some of the carbon dioxide to the atmosphere. Moreover, the oxygen produced by the photosynthesis reactions is not recoverable. Because of these disadvantages, the use of photobioreactors is a preferred means of using carbon dioxide.
Current world-wide research and development work in algae cultivation is largely based on the use of a diluted form of carbon dioxide in combustion gases from fossil energy power generating installations and its direct transport to algae cultivation installations. Emerging development in fossil-energy based power generating systems such as oxyfuel combustion promises by-product streams of virtually 100% content (neat) carbon dioxide as contrasted with the about 13-15 volume % conventional carbon-dioxide content in chimney gases. Chemical reaction rates in the photosynthesis process, like all chemical reactions, increase markedly when there is an excess of a key reactant, which the neat carbon dioxide can facilitate.
Given surpluses in the reactants, carbon dioxide and water, reaction rates will be determined by the availability of photons from insolation.